JP2002313741A - GaN BASED COMPOUND SEMICONDUCTOR CRYSTAL AND ITS MANUFACTURING METHOD - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for effectively restraining generation of contamination in a manufacturing method of GaN based compound semiconductor crystal wherein a rare earth 13 (3B) group perovskite is used as a substrate. SOLUTION: In a method wherein GaN based compound semiconductor crystal is grown on the surface of a substrate in which a rare earth 13 (3B) group perovskite crystal containing one or at least two kinds of rare earth elements is used, at least the back of the substrate is coated with SiO2 . Thereby the are earth elements as constituent elements of the substrate are prevented from being captured during crystal growth.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a semiconductor device such as a light emitting device or an electronic device.
The present invention relates to a method for producing an aN-based compound semiconductor crystal.

[0002]

2. Description of the Related Art GaN, InGaN, AlGaN, InGaN
GaN-based compound such as GaAlN semiconductor _(In x _Ga y A
l _1-xy N where 0 ≦ x, y; x + y ≦ 1) is expected as a material for semiconductor devices such as electronic devices such as light emitting devices and power devices, and as a material applicable in various other fields. Attention has been paid.

Conventionally, it has been difficult to grow a bulk crystal of a GaN-based compound semiconductor. For this reason, the above-mentioned electronic device has a substrate on which a thin-film single crystal such as GaN is formed by heteroepitaxy on a heterogeneous crystal such as sapphire. Was used.

However, since the lattice mismatch between the sapphire crystal and the GaN-based compound semiconductor crystal is large, the dislocation density of the GaN-based compound semiconductor crystal grown on the sapphire crystal becomes large and crystal defects occur. was there. Furthermore, since sapphire has a low thermal conductivity and is difficult to dissipate heat, there is a problem in that when a substrate in which a GaN-based compound semiconductor crystal is grown on a sapphire crystal is used for an electronic device or the like which consumes a large amount of power, the temperature tends to rise.

Accordingly, the need for a substrate having a large thermal conductivity and lattice-matching with a GaN-based compound semiconductor crystal has been further increased.
Research such as ELO (Epitaxial Lateral Overgrowth) using hydride vapor phase epitaxy (hereinafter abbreviated as HVPE) has been rapidly advanced. Here, the ELO method means that, for example, an insulating film serving as a mask is formed on a sapphire substrate, an opening is provided in a part of the insulating film, the insulating film is used as a mask, and the exposed sapphire substrate surface is subjected to epitaxial growth. This is a method of growing a GaN-based compound semiconductor crystal having high crystallinity. According to this method, the growth of the GaN-based compound semiconductor crystal starts from the surface of the sapphire substrate inside the opening provided in the mask, and the growth layer spreads on the mask, so that the dislocation density in the crystal can be suppressed to a small value. Thus, a GaN-based compound semiconductor crystal having few crystal defects can be obtained.

However, since the GaN-based compound semiconductor crystal obtained by the ELO method has a large thermal strain, the sapphire substrate is separated by polishing in the wafer manufacturing process so that the
There is a problem that the GaN-based compound semiconductor crystal wafer is distorted when trying to obtain the aN-based compound semiconductor crystal wafer alone.

Therefore, the present inventors have used a rare earth 13 (3B) group perovskite crystal as one of the materials for the heterocrystalline substrate, and have grown a GaN-based compound semiconductor using the {011} plane or the {101} plane as a growth plane. A method of growing by heteroepitaxy was proposed (WO 95/278).
No. 15). The {011} plane or {10}
The 1｝ plane represents a set of planes equivalent to the (011) plane and the (101) plane, respectively.

According to the growth technology of the prior application, for example, NdGa which is one of the rare earth 13 (3B) group perovskites is used.
Using O ₃ as a substrate, its {011} plane or {101}
When GaN is grown on a surface, the lattice mismatch is about 1.2%, which is much smaller than that of a substrate made of sapphire or SiC used as a substitute thereof. Therefore, the dislocation density in the crystal is reduced, so that a GaN-based compound semiconductor crystal with few crystal defects can be grown.

[0009]

However, in the growth method of the prior application, when growing a GaN-based compound semiconductor crystal, the occurrence of crystal defects due to lattice mismatch with the substrate could be suppressed. There is a problem in that contamination (contamination) occurs in the GaN-based compound semiconductor crystal, thereby deteriorating the crystallinity and adversely affecting the device characteristics of the semiconductor element.

An object of the present invention is to provide a method of manufacturing a GaN-based compound semiconductor crystal using a rare-earth 13 (3B) group perovskite as a substrate, and to provide a technique for effectively suppressing generation of contamination.

[0011]

According to the present invention, in order to achieve the above object, a rare earth 13 (3B) group perovskite crystal containing one or more kinds of rare earth elements is used as a substrate and its surface (one main surface) is formed. In the method for growing a GaN-based compound semiconductor crystal, at least the back surface of the substrate is made of Si.
And so as to cover at O _2.

Thus, the rare earth element can be prevented from being decomposed on the back surface of the rare earth 13 (3B) group perovskite crystal substrate, so that the decomposed rare earth element can effectively prevent contamination of the GaN-based compound semiconductor crystal. Can be prevented.

Further, Al, G as a group 13 (3B) element
rare earth 13 containing at least one of a and In
The present invention can be applied to a case where a (3B) group perovskite crystal, for example, an NdGaO ₃ crystal is used as a substrate.

Preferably, the GaN compound semiconductor crystal is formed on the substrate by a hydride VPE method.

Further, the thickness of the SiO ₂ is 0.1 to 1
By setting the thickness to 0 μm, the decomposition of rare earth elements, for example, Nd from the back surface of the substrate can be effectively suppressed.

A GaN-based compound semiconductor crystal having an Nd concentration of less than 1.0 × 10 ¹⁶ cm ⁻³ and a half-width of an X-ray rocking curve of less than 0.25 ° obtained by the above-described manufacturing method is used for a semiconductor device. It is suitable as a material.

Hereinafter, the process of completing the present invention will be described. First, the present inventors have noticed that some of the GaN-based compound semiconductor crystals obtained by the method for growing a GaN-based compound semiconductor crystal proposed in the above-mentioned prior application have poor crystallinity. That is, in the above-described growth method, the generation of crystal defects due to lattice mismatch with the substrate when growing the GaN-based compound semiconductor crystal could be suppressed, but the crystallinity of the obtained GaN-based compound semiconductor crystal deteriorated. Therefore, it has been found that it is difficult to put it into practical use as a method for producing a GaN compound semiconductor crystal suitable for a material of a semiconductor device.

Therefore, the present inventors consider that there is room for further improvement in the above-mentioned growth method, and have intensively studied to improve the crystallinity of the GaN-based compound semiconductor crystal obtained by the above-mentioned growth method.

First, the present inventors obtained the above-mentioned growth method.
Causes the crystallinity of GaN compound semiconductor crystals to deteriorate
investigated. As a result, the GaN compound semiconductor crystal
It turns out that termination has occurred,
It was confirmed that the crystallinity was deteriorated. And book
We have NdGaO₃Nd, a constituent element of the substrate,
It is presumed that contamination occurs in the crystal due to
Was. That is, NdGaO ₃Ga in the substrate is Ga₂O₃What
Which oxide will volatilize, but Nd oxide is safe.
GaN-based compound
Reduced to hydrogen generated during the growth reaction of the semiconductor crystal
Was thought to be easily incorporated into the crystal.

Next, the relationship between the Nd concentration in the crystal and the crystallinity will be described.
To investigate, NdGaO₃GaN compound half on substrate
By growing the conductor crystal under different growth conditions, the Nd concentration
1.0 × 10¹⁷~ 1.1 × 10¹⁸cm^-3In the range
Certain samples were obtained. The Nd concentration is a secondary ionic
O in bulk analysis (semi-quantitative value) by quantitative analysis (SIMS)
₂It was measured using ions.

When the full width at half maximum (FWHM) of the X-ray rocking curve (XRC) was measured for these samples, the results shown in FIG. 1 were obtained, and there was a correlation between the Nd concentration and the FWHM. I understood. From this, it was confirmed that the crystallinity was improved when the Nd concentration in the crystal was reduced. In FIG. 1, ▲ marks (A) to (C) are plots of FWHM values obtained by measuring the samples obtained under the above conditions.

The present inventors further measured the Nd concentration and FWHM when a GaN compound semiconductor crystal was grown on a sapphire substrate under the same growth conditions under the same growth conditions. As a result, the Nd concentration is 2.3 × 10 ¹⁵ cm.
^-3 and the contamination by Nd is NdGaO
₃ was smaller than when the substrate was used.
However, since the lattice mismatch between the sapphire crystal and the GaN compound semiconductor crystal was large, the FWHM was large and the crystallinity was poor (mark (D) in FIG. 1).

From this experiment, it was found that NdGaO ₃ substrate
Was decomposed and taken into the GaN compound semiconductor crystal to cause contamination. Than this,
If Nd decomposed from the NdGaO ₃ substrate is suppressed, Ga
It has been obtained that Nd contamination can be prevented from occurring in the N-compound semiconductor crystal, and the crystallinity can be improved.

[0024] and then, in order to suppress the NdGaO ₃ substrate of Nd it is degraded, an experiment was conducted for growing a GaN compound semiconductor crystal with a NdGaO ₃ substrate coated backside with SiO _2. As a result, GaN
The Nd concentration in the compound semiconductor crystal is 5.4 × 10 ¹⁵ cm
^−3, which was extremely small, and Nd was prevented from being taken into the crystal by coating the back surface with SiO ₂ . The FWHM of the GaN compound semiconductor crystal
Was 0.18 °, and crystals excellent in crystallinity could be obtained, as the present inventor's opinion (indicated by ● (E) in FIG. 1).

The present invention has been made on the basis of the above-described findings, and has been proposed for a semiconductor device by coating the back surface with SiO ₂ when epitaxially growing a GaN-based compound semiconductor crystal on the surface of a rare earth 13 (3B) group perovskite substrate. Suitable high-quality GaN compound semiconductor single crystals can be grown.

It is to be noted that the present invention relates to a method in which Ga is added to an NdGaO ₃ substrate.
Although it was found by an experiment for growing an N compound semiconductor crystal, in addition to the GaN compound semiconductor crystal, In
It is considered that a similar effect can be obtained when a GaN-based compound semiconductor crystal such as GaN or AlGaN is grown. As the rare earth 13 (3B) group perovskite crystal substrate, in addition to NdGaO ₃ , NdAlO ₃ and NdInO ₃
Etc. can be used.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION A preferred embodiment of the present invention will be described below in which a GaN compound semiconductor crystal is grown using an NdGaO ₃ crystal as a substrate.

(Example) First, an ingot of NdGaO ₃ was sliced to obtain a substrate for crystal growth. At this time,
The size of the NdGaO ₃ substrate is 50 mm in diameter, and the thickness is 0.1 mm.
It was 5 mm.

Next, 3 μm of SiO ₂ was applied to one surface of the substrate using a sputtering apparatus, and the other surface was used as a crystal growth surface.

Next, the mirror-polished NdGaO ₃ substrate was subjected to ultrasonic cleaning in acetone for 5 minutes, followed by ultrasonic cleaning in methanol for 5 minutes. Thereafter, the liquid droplets were blown off by blowing with N ₂ gas, and then air-dried. next,
The washed NdGaO ₃ substrate was etched with a sulfuric acid-based etchant (phosphoric acid: sulfuric acid = 1: 3, 80 ° C.) for 5 minutes.

Next, the NdGaO ₃ substrate is placed at a predetermined position in a hydride VPE apparatus with the SiO ₂ coated surface as a back surface, and the substrate temperature is reduced to 6 while introducing N ₂ gas.
The temperature was raised to 20 ° C., and GaCl generated from Ga metal and HCl gas, and NH ₃ gas were supplied onto the NdGaO ₃ substrate using an N ₂ carrier gas, and Ga Ga of about 100 nm was supplied.
An N protective layer was formed. Since NdGaO ₃ reacts with NH ₃ or H ₂ at a high temperature of 800 ° C. or more to generate a neodymium compound, N ₂ Ga is used as a carrier gas in this embodiment.
And forming a protective layer at a low growth temperature of 620 ° C. so that a neodymium compound is not generated.

Next, the substrate temperature was raised to 1000 ° C.
a GaCl generated from metal and HCl gas, NH
_{The three} gases were supplied onto a NdGaO ₃ substrate using a N ₂ carrier gas. At this time, the GaCl partial pressure is 5.0 × 10
^-40 atm while controlling the gas introduction amounts so that the ^-3 atm and the NH ₃ partial pressure are 3.0 × 10 ⁻¹ atm.
A GaN compound semiconductor crystal was grown at a growth rate of m / h for 300 minutes.

Thereafter, a cooling rate of 5.3 ° C./min
After cooling for one minute, a GaN compound semiconductor crystal having a thickness of about 200 μm was obtained.

The obtained GaN compound semiconductor crystal has Nd
The concentration is 5.4 × 10 ¹⁵ cm ⁻³ and the FWHM is 0.1
It was a single crystal with excellent crystallinity of 8.

(Comparative Example 1) Next, as a comparative example, NdGa
The same crystal growth as in the above example was performed without coating the back surface of the O ₃ substrate with SiO ₂ .

In Comparative Example 1, a crystal was grown using a substrate obtained by slicing an NdGaO ₃ ingot as it was. At this time, the size of the NdGaO ₃ substrate was the same as that of the example, and the cleaning of the substrate was the same as that of the example.

When a GaN compound semiconductor crystal was grown using this substrate, the obtained GaN compound semiconductor crystal had an Nd concentration of 1.0 to 1.3 × ¹⁷ cm ^−3, which was smaller than that of the example. It was larger than an order of magnitude. The FWHM is 0.1.
4 to 0.83, and the crystal quality was inferior to that of the examples.

Comparative Example 2 In Comparative Example 2, a GaN compound semiconductor crystal was grown at a growth temperature of 1100 ° C. using the same substrate as in Comparative Example 1. However, all the growth conditions other than the growth temperature were the same as in the example.

The GaN compound semiconductor crystal obtained in Comparative Example 2 has an Nd concentration of 6.8 × 10 ^{17 to} 5.9 × 10 ^18.
cm ^-3 . This is probably because the crystal was grown at a higher temperature in Comparative Example 2 than in Comparative Example 1, so that Nd was easily decomposed from the NdGaO ₃ substrate, and the Nd concentration in the crystal was increased. In addition, G obtained in Comparative Example 2
The FWHM of the aN compound semiconductor crystal was around 1.2, and the crystal quality was inferior to that of the example.

Although the invention made by the inventor has been specifically described based on the embodiment, the invention is not limited to the above embodiment. For example, NdGaO
_As a material for coating the back surface of the _three substrates, other than SiO ₂ , SiC, pBN, or the like can be used. The present invention is not limited to the case where a GaN compound semiconductor crystal is grown. For example, a similar effect can be obtained by applying the present invention to a method of growing a GaN compound semiconductor crystal such as InGaN or AlGaN. Also, rare earth 1 used as a substrate
The 3 (3B) group perovskite crystal is not limited to NdGaO ₃ crystal, and for example, NdAlO ₃ , NdInO ₃ or the like can be used.

The crystal growth conditions include a GaCl partial pressure of 1.0 × 10 ^{−3 to} 1.0 × 10 ⁻² atm, NH 3
₃ partial pressures of 1.0 × 10 ^{−1 to} 4.0 × 10 ⁻¹ atm,
Growth rate is 30 ~ 100μm / h, growth temperature is 930
It is desirable that the cooling rate is 4 to 10 ° C./min.

[0042]

According to the present invention, there is provided a method for growing a GaN-based compound semiconductor crystal on the surface of a rare earth 13 (3B) group perovskite crystal containing one or more rare earth elements as a substrate. Since the back surface is coated with SiO ₂ , the decomposition of the rare earth element (for example, Nd) on the back surface of the substrate can be suppressed, so that contamination of the GaN-based compound semiconductor crystal by the decomposed rare earth element can be reduced. And the crystallinity of the GaN-based compound semiconductor crystal can be improved.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the Nd concentration in a GaN compound semiconductor crystal and the half width of an X-ray rocking curve.

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[Procedure amendment]

[Submission date] June 29, 2001 (2001.6.2
9)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction contents]

The obtained GaN compound semiconductor crystal has Nd
The concentration is 5.4 × 10 ¹⁵ cm ⁻³ and the FWHM is 0.1
It was a single crystal having excellent crystallinity of 8 ° .

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0037

[Correction method] Change

[Correction contents]

When a GaN compound semiconductor crystal was grown using this substrate, the obtained GaN compound semiconductor crystal had an Nd concentration of 1.0 to 1.3 × ¹⁷ cm ^−3, which was smaller than that of the example. It was larger than an order of magnitude. The FWHM is 0.1.
4 to 0.83 ° , and the crystal quality was inferior to the examples.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0039

[Correction method] Change

[Correction contents]

The GaN compound semiconductor crystal obtained in Comparative Example 2 has an Nd concentration of 6.8 × 10 ^{17 to} 5.9 × 10 ^18.
cm ^-3 . This is probably because the crystal was grown at a higher temperature in Comparative Example 2 than in Comparative Example 1, so that Nd was easily decomposed from the NdGaO ₃ substrate, and the Nd concentration in the crystal was increased. In addition, G obtained in Comparative Example 2
The FWHM of the aN compound semiconductor crystal was around 1.2 ° , and the crystal quality was inferior to that of the example.

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Claims (6)

[Claims] 1. A method for growing a GaN-based compound semiconductor crystal on a surface of a rare earth 13 (3B) group perovskite crystal containing one or more rare earth elements, wherein at least the back surface of the substrate is covered with SiO ₂ . A method for producing a GaN-based compound semiconductor crystal. 2. The rare earth element 13 used as a substrate.
13 (3B) constituting a (3B) group perovskite crystal
The method according to claim 1, wherein the group III element is at least one of Al, Ga, and In. 3. The method according to claim 2, wherein the rare earth 13 (3B) group perovskite crystal substrate is a NdGaO ₃ crystal. 4. The Ga according to claim 1, wherein the GaN-based compound semiconductor crystal is formed on the substrate by a hydride VPE method.
A method for producing an N-based compound semiconductor crystal. 5. The thickness of the SiO ₂ is 0.1 to 10 μm.
The method for producing a GaN-based compound semiconductor crystal according to claim 1, wherein m is m. 6. The Nd concentration is less than 1.0 × 10 ¹⁶ cm ⁻³ , and the half width of the X-ray rocking curve is 0.25 °.
A GaN compound semiconductor crystal for a semiconductor device, wherein